Nonfat dried milk moisture content

FIG. 17 Water activity (or relative vapor pressure) and moisture content (%, wb) values plotted for a variety of food materials ( as is ), resulting in a composite (or universal) food isotherm. Potato chip and nonfat dry milk (NFDM) data are from van den Berg (1986). All other data are from the author s laboratory (at 20 or 25 1 °C). Water activity and moisture content values for the breakfast cereal and fruit and vegetable categories had the largest ranges (expressed here as standard deviation) 0.311 0.073 aw and 2.94 1.55% me (wb) and 0.995 0.004 aw and 89.8 3.90% me (wb), respectively. The curve is to guide the eye—it is not a fitted line. 

Most dry buttermilk is prepared from sweet cream buttermilk, and is produced in a manner similar to that of nonfat dry milk. Dry buttermilk has a higher phospholipid content than other dry milk products and therefore is a natural emulsifier for use in the dairy and baking industries and for dry mixes and other foods. A dry, high-acid buttermilk can be produced from milk fermented by L. bulgaricus. It is difficult to dry, however, and has found only limited use in the baking industry. There are no United States and FAO standards for this product, although typically the moisture content is less than 5%. 

At the same time, Baer et al. (1) determined water content, protein, and fat in commercial skim milk powders and in the laboratory prepared from nonfat dry milk (NFDM) samples. They used 44 commercial low-, medium-, and high-heat samples and 38 laboratory prepared samples, to increase the composition range. Data indicated that prediction of moisture content by NIR was linear throughout the tested range (2.85-9.70%). They reported that usable predictions of composition could be obtained even when physical factors such as particle size were not constant. They also concluded that NIR calibrations at individual dairy plants probably result in lower SEP values because of the greater physical homogeneity of samples. 

Nonfat dry milk—This product is prepared by removing water from pasteurized skim milk. Federal standards of Identity require that It contain not more than 5% by weight of moisture and not more than 1.5% by weight of milkfat unless Indicated. Except for small losses of ascorbic acid, thiamin, vitamin B-12, and biotin, the processing has no appreciable effect on the nutritive value of the milk. Due to Its low moisture content. It can be kept for long periods. 

FIGURE 39.17 Effect of the protective substance s medium on the survival rate of Lactobacilli at various dr dng times (1) adonitol (2) glutamate (3) PEG 1000 and (4) nonfat skim milk. (From C.F. De Valdez, G.S. De Giori, and A.P. De Ruiz Holgado, Effect of Dr dng Medium on Residual Moisture Content and Viability of Freeze-Dried Lactic Acid Bacteria, Applied and Environmental Microbiology, 49, 413-415 (1985). With permission.)... 

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